1. Field of the Invention
The present invention relates to an integrated process for the selective dimerization of isobutylene and especially to the use of isooctane formed by diisobutylene hydrogenation as a dimerization solvent. Especially advantageous features include the use of tertiary butanol as from the Oxirane propylene oxide/tertiary butanol process as feed and the provision of tertiary butanol as a selectivity enhancing modifier during the dimerization.
2. Description of the Prior Art
The oligomerization of olefins such as isobutylene using acidic catalysts is a known reaction.
As described in U.S. Pat. No. 3,760,026, a number of catalysts are known for this reaction including cold sulfuric acid, phosphoric acid on Kieselguhr, silica/alumina sometimes promoted with Ni, Co, Fe, Pt or Pd; activated natural clays plus activating substances such as ZnO metallic phosphates such as those of iron (III) and cerium optionally supported on carriers such as activated carbon, bauxite, activated carbon alone and with metal haliders such as TiCl.sub.2 heteropolyacids such as silicotungstic acid on silica gel and phosphomolybdic acid; BF.sub.3 H.sub.3 PO.sub.4 and BF.sub.3 HPO.sub.3 ; dihydroxyfluroboric acid HF and fluorides or oxyfluorides of S, Se, N, P, Mo, Te, W, V and Si boiling below 300.degree. C.; BF.sub.3 dimethyl ether complexes; BF.sub.3 hydrocarbon complexes; BF.sub.3 SO.sub.2 ; and AlCl.sub.3 with cocatalysts such as dimethyl ether, HCl, and nitromethane. These catalysts and dimerization processes, including operating conditions, are known in the art.
An especially preferred catalyst is a sulfonic acid-type ion exchange resin such as Amberlyst A-15. U.S. Pat. No. 4,447,668 describes isobutylene dimerization using A-15 with methyl t-butyl ether as solvent.
Considerations associated with the isobutylene dimerization involve removal of the substantial heat of reaction and the requirement that high selectivity to the dimer product be maintained. The instant invention provides a process wherein these objectives are achieved.